Dielectric measurement of a biological cell at microwave frequency or optical frequency provides unique yet distinct information about its physiological state. Microwave dielectric spectroscopy gives information on plasma membrane complexity and permeability, cytoplasm and nucleoplasm ion concentration, and the presence of smaller membrane-bound organelles. Optical holographic imaging and reconstruction provides complementary information on cell morphology and refractive index, which reflects cytoplasm and nucleoplasm mass density. As shown in Fig. 1a, we use a microfluidic device for dual-modality RF dielectrophoresis (DEP) and optical scattering measurements of single biological cells while in flow. (E. Kovacs, et al., “Light-Emitting Diode Array with Optical Linear Detector Enables High-Throughput Differential Single-Cell Dielectrophoretic Analysis,” Sensors, vol. 24, issue 24, 8071, 2024). Cells flow through a channel and over electrodes, which induce an RF frequency-dependent DEP force that translates them vertically to higher or lower velocity regions in the channel. Multiple LED semi-coherent optical sources above the channel illuminate the cells. A linear CMOS imaging array below the channel captures the resulting inline incident-scattered field interference patterns. The captured holograms are analyzed to reconstruct each cell's size and optical refractive index. Simultaneously, the cell's DEP induced velocity trajectory, obtained by particle tracking, is used to analyze selected RF dielectric properties. (S. Afshar, et al., “Full Beta-Dispersion Region Dielectric Spectra and Dielectric Models of Viable and Non-Viable CHO Cells,” IEEE J. Electromagnetics, RF, Microwaves in Medicine and Biology, vol. 5, issue 1, 2021).

This paper presents a lens-free imaging approach utilizing an array of light sources, capable of measuring the dielectric properties of many particles simultaneously. This method employs coplanar electrodes to induce velocity changes in flowing particles through dielectrophoretic forces, allowing the inference of individual particle properties from differential velocity changes. Both positive and negative forces are detectable. The light source utilized in this system is composed of LEDs with a wavelength of 470 nm, while detection is performed using a 256-element optical array detector. Measurements with 10 μm polystyrene beads demonstrate this method can resolve changes equivalent to a Clausius–Mossotti factor of 0.18. Simulations in this work, using values from the literature, predict that Clausius–Mossotti factor differences of 0.18 are sufficient to differentiate viable from nonviable cells and cancerous from multidrug-resistant cancerous cells. We demonstrate that for Chinese hamster ovary (CHO) cells, the method can collect a dielectric response spectrum for a large number of cells in several minutes. We demonstrate that for CHO cells, Clausius–Mossotti factor differences of 0.18 can be discriminated. Due to its simple detection apparatus and the utilization of high-throughput, wide, clog-resistant channels, this method holds promise for a wide range of applications.

Civil structural health monitoring (CSHM) tracks different aspects of an infrastructure system’s service and safety condition by utilizing reliably measured data and physics-based model simulations. Data and physical models are coupled with heuristic experience to proactively represent current and expected future performance. In the past two decades, more bridges and dams have been instrumented and monitored during and after construction to determine their performances and responses to various loading, material, boundary, and environmental conditions. Furthermore, bridge and dam owners increasingly utilize civionics systems to obtain essential data for developing data-driven asset management programs and addressing the state of good repair requirements.

In this paper, we present a microfluidic flow cytometer for simultaneous imaging and dielectric characterization of individual biological cells within a flow. Utilizing a combination of dielectrophoresis (DEP) and high-speed imaging, this system offers a dual-modality approach to analyze both cell morphology and dielectric properties, enhancing the ability to analyze, characterize, and discriminate cells in a heterogeneous population. A high-speed camera is used to capture images of and track multiple cells in real-time as they flow through a microfluidic channel. A wide channel is used, enabling analysis of many cells in parallel. A coplanar electrode array perpendicular to cell flow is incorporated at the bottom of the channel to perform dielectrophoresis-based dielectric characterization. A frequency-dependent voltage applied to the array produces a non-uniform electric field, translating cells to higher or lower velocity depending on their dielectric polarizability. In this paper, we demonstrate how cell size, obtained by optical imaging, and DEP response, obtained by particle tracking, can be used to discriminate viable and non-viable Chinese hamster ovary cells in a heterogeneous cell culture. Multiphysics electrostatic-fluid dynamics simulation is used to develop a relationship between cell incoming velocity, differential velocity, size, and the cell's polarizability, which can subsequently be used to evaluate its physiological state. Measurement of a mixture of polystyrene microspheres is used to evaluate the accuracy of the cytometer.

The internal micro-structure of glass and carbon fibre-reinforced polymer (FRP) rebars subjected to tensile loading was investigated using micro computed tomography (μCT) and scanning electron microscopy (SEM) images. Three dimensional (3D) and two dimensional (2D) reconstructed μCT images were used to study and quantify the void volume and its distribution along with FRP rebar samples after being subjected to tensile loads. The void volume was observed to increase in all samples as the tensile load on the samples was increased. Acoustic emission (AE) monitoring during the tensile loading was also employed to establish a correlation between the AE parameters and damage evolution in the FRP samples. Cumulative energy of AE signal in frequency domain was used to monitor the progression of the internal damage in the FRP reinforcing rebars. A high correlation was observed between the void volume measured by μCT and SEM and the cumulative energy of the AE signal.

Bulk electrical impedance spectroscopy (bio-capacitance) probes, hold significant promise for real-time cell monitoring in bioprocesses. Focusing on Chinese hamster ovary (CHO) cells, we present a sensitivity analysis framework to assess the impact of cell and culture properties on the complex permittivity spectrum, εmix, and its associated parameters, permittivity increment, Δε, critical frequency, fc, and Cole-Cole parameter, α, measured by bio-capacitance probes. Our sensitivity analysis showed that Δε is highly sensitive to cell size and concentration, making it suitable for estimating biovolume during the exponential growth phase, whereas fc provides information about cumulative changes in cell size, membrane permittivity, and cytoplasm conductivity during the transition to death phase. The analysis indicated that specific information about cell membrane permittivity or internal conductivity cannot be extracted from εmix spectrum. Based on the sensitivity analysis, we proposed two alternative parameters for monitoring cells in bioprocesses: Δε1 MHz and Δε1 MHz/Δε0.3 MHz, using measurements at 300 kHz, 1 MHz, and 10 MHz. Δε1 MHz is suitable for estimating viable cell density during the exponential growth phase due to its lower sensitivity to cell size. Δε1 MHz/Δε0.3 MHz can replace fc due to similar sensitivities to cell size and dielectric properties. These frequencies are within most bio-capacitance probes' optimal operation range, eliminating the need for low-frequency electrode polarization and high-frequency stray capacitances corrections. Experimental measurements on CHO cells confirmed the results of sensitivity analysis.

Steel tendons commonly used in pre-stressed/post-tensioned concrete structural systems can lose cross-section due to corrosion, eventually leading to acoustic emission (AE) events when the stress exceeds the breaking strength of the wires that make up the tendons. Reliable differentiation of wire break AE events from traffic or grout crack events is critical for monitoring large structures, even where the distance between sensors may produce highly attenuated signals. In this paper, the Fuzzy c-means clustering algorithm was employed to differentiate AEs released from breaking wires of steel tendons from a database of 13464 AEs, including wire breaks, environmental and grout crack AEs. Wire breaks and grout crack AEs were collected from axial loading tests of grouted tendons in which the load increased until a wire broke. Environmental acoustic signals were collected from a bridge. Then all the collected AEs were gathered in a database and post-processed to simulate attenuation of up to 20 m from source to sensor. To optimize the speed and reliability of the Fuzzy c-means clustering algorithm, a non-dominated sorting genetic algorithm-II (NSGA-II) was used to find the minimum number of acoustic features needed. The NSGA-II algorithm started with 201 possible acoustic features and found 12 combinations of features that resulted in more than 80% wire break detection accuracy. In contrast, less than 3% of grout cracks and 0% of environmental signals were detected as wire breaks. The proposed method is suitable for deployment in a large sensor network and has sufficiently low-computational requirements for at-the-sensor processing, eliminating the need to send high-frequency sampled data outside the sensor node.

Faults in a grounding network pose a serious threat to power system equipment protection and worker safety. A large number of vertical electrodes is used in a grounding network and break-points in these due to soil induced corrosion is one of the prime reasons for faults. We present a rod insertion time domain reflectometry (TDR) technique for vertical grounding electrode break-point detection. A secondary bare rod is inserted adjacent to the grounding electrode while a fast risetime pulse is continuously applied to excite a transverse electromagnetic (TEM) wave that propagates along the rods and reflects back from the break-point. The reflected signals for different depths of the secondary rod are analyzed to identify the location and severity of the break-point. We show that fault detection is possible without prior knowledge of soil electrical parameters. To show the feasibility of the proposed technique, a full wave simulation approach is used to evaluate the wideband input impedance of the grounding and inserted rod system and then FFT is applied to obtain TDR responses. The results show the method is capable of detecting faults for a wide range of soil conductivity for a system bandwidth of 300 MHz.

Acoustic sensors attached to pre-stressed/post-tensioned bridges are promising tools for monitoring the progression of corrosion damage in pre-stressing/post-tensioning tendons. In this study, acoustic emission signals from a pre-stressed beam containing three pre-stressed tendons that were exposed to accelerated corrosion conditions were studied. A short length of each tendon was exposed, and a tank filled with the NaCl solution was placed over the exposed tendon. Over a period of several months, a corrosion current was driven into the tendons until at least one wire corroded through. Acoustic sensors were attached along the beam and were used to record acoustic emission events during the accelerated corrosion. At the termination of the accelerated corrosion experiment, the beam was sliced into sixty-two cross-sections, each being 5 cm thick. Each slice was inspected to correlate corrosion and tendon slippage with acoustic emission signals. Maps of the estimated origin of acoustic emission signals were compared with the maps of the position of tendon corrosion and slippage. The acoustic emission signals were correlated with the presence of wire fracture due to corrosion on the tendon and with proximity to the end of the beam. The larger emission signals are likely due to the loss of bond between the tendons and concrete, as tendon fracture due to corrosion was not found in any of the cross-sections. This work points to the use of acoustic emission to track the progression of damage in cases where corrosion has already resulted in tendon fracture, and progression is proceeding by loss of bond.

The ability to quantitatively and non-invasively characterize complex multiphase geomaterials is still a major challenge to the engineering, construction, and geophysical fields. In the context of accelerating climate change, construction on permafrost requires remedial measures and an appropriate characterization of permafrost (e.g., ice content, unfrozen water content, porosity, ice lenses, soil type, and mechanical properties). Current techniques are insufficient for efficient characterization of permafrost samples. Here, we propose an ultrasonic sensing technique and a signal interpretation method based on an inverse multiphase poromechanical approach to overcome critical gaps in permafrost characterization. This technique allows us to interpret the measured electrical signal using a theoretical transfer function obtained through an efficient multiphase poromechanical forward solver. Our study demonstrates the potential of the ultrasonic sensing technique for the rapid characterization of permafrost samples in terms of both physical and mechanical properties.

Soil scour near a bridge pier foundation is one of the leading causes of bridge failures. Traditional vibration-based scour monitoring methods are nearly incapable of quantifying scour levels using a single acceleration response without knowledge of excitation information. In this paper, a new output-only scour level prediction method is introduced via the integration of an unscented Kalman filter (UKF), random decrement (RD), and newly derived continuous Euler–Bernoulli beam addressing river water, traffic loads, and the linear and nonlinear behavior of sediments around the pier as external effects. We conducted extensive simulation studies and applied the method to an existing medium-span bridge with a steel girder and concrete deck in service in the province of Manitoba, Canada. These studies show that our proposed method can accurately estimate scour levels using only one accelerometer, which was validated with an independent bathymetric survey of the soil level at the pier foundation. Furthermore, three different linear and nonlinear soil profiles representing the soil behavior around the pier were also investigated as case studies in the scour level estimation process. The results confirm that a cubic function exhibits the best performance in quantifying the scour level around bridge piers.

Reducing greenhouse gas emissions including carbon dioxide (CO2) is central to minimizing the human contribution to global warming. Industrial activities and transportation are some of the main contributors to carbon dioxide emission. Bridges are the key element in the transportation system and many of them are reaching the end of their designed service life. Replacing bridges requires a significant amount of construction materials and equipment, which will lead to significant carbon dioxide emissions. In this work, we conclude that carbon dioxide emission can be reduced by applying structural health monitoring (SHM) instrumentation and techniques to bridge management. In this work, two medium span steel girder bridges have been used to study the impact of the application of SHM on the emitted carbon dioxide. From two monitored bridges traffic load strains were used to monitor the load distribution factor and neutral axis position of each girder. This data can be used to extend the service life of these bridges. By extending the service life of a bridge, the average annual carbon dioxide emission associated with the bridge is reduced. Considering the emission due to material production and construction, the carbon dioxide emission due to bridge reconstruction will decrease by 9–17% under the assumption that the application of SHM will extend the service life of a bridge by 5–10 years. Data from Federal Highway Administration (FHWA) for the state of Iowa, which includes the number of structurally deficient bridges, was used to estimate the short-term and long-term cumulative CO2 emission for a fleet of bridges. It was concluded that if all structurally deficient bridges (rating 3 or less) in Iowa were replaced for the 2000–2019 time period, the cumulative CO2 emission would have been 4,38,483 tonnes. However, if SHM were to be applied and extended the service life of 80% of these bridges by 5 or 10 years the total emission would have been reduced to 2,84,048 tonnes or 1,75,695 tonnes.

The dielectric properties of biological cells can be used to gain information on their physiology and morphology. This paper reports the first measurements of the dielectric spectra of viable and non-viable cells over the full beta-dispersion (interfacial) frequency range. Dielectrophoresis (DEP) single cell in-flow techniques were employed to quantitatively measure the Clausius-Mossotti factor spectrum of individual cells over the 300 kHz-400 MHz range, covering both the MF and UHF DEP cross-over frequencies. Experiments were performed on Chinese hamster ovary (CHO) cells, one set cultured in growth media, the other in nutrient depleted media to induce apoptotic cells. Both cell states were measured using multi-frequency DEP flow cytometry, which provides the equivalent complex dielectric permittivity of individual cells. The measured dielectric spectra facilitate determination of a cell's morphology and the dielectric properties of its intracellular compartments, and are used to develop multi-shell dielectric models of viable and non-viable cells. The developed dielectric models can aid in biosensor design, in interpretation of bulk biomedia measurements where the heterogeneity in cell population can be masked, and in relating measured dielectric responses of cells to stimuli with changes in cellular physiology.

Fibre reinforced polymer (FRP) rods are widely used as corrosion-resistant reinforcing in civil structures. However, developing a method to determine the loads on in-service FRP rods remains a challenge. In this study, the entropy of acoustic emission (AE) emanating from FRP rods is used to estimate the applied loads. As loads increased, the fraction of AE hits with higher entropy also increased. High entropy AE hits are defined using the one-sided Chebyshev’s inequality with parameter k = 2 where the histogram of AE entropy up to 10–15% of ultimate load was used as a baseline. According to the one-sided Chebyshev’s inequality, when more than 20% (k = 2) of AE hits that fall further than two standard deviations away from the mean are classified as high entropy events, a new distribution of high entropy AE hits is assumed to exist. We have found that the fraction of high AE hits. In glass FRP and carbon FRP rods, a high entropy AE hit fraction of 20% was exceeded at approximately 40% and 50% of the ultimate load, respectively. This work demonstrates that monitoring high entropy AE hits may provide a useful means to estimate the loads on FRP rods.

Acoustic pulse-echo systems, are effective for corrosion damage detection in buried individual ground rods without any need for excavation. In electric power distribution systems there are large numbers buried ground rods are used in substations to form a grounding networks that is critical for the protection of equipment and personnel working in the vicinity of the substation. Over time, these grounding rods will corrode and cease to provide adequate protection. In this work, we present an equivalent circuit model (ECM) for acoustic pulse-echo corrosion detection systems. The circuit model was used to develop a transducer configuration that effectively launches longitudinal acoustic waves that can accurately detect position and damage severity. We show that our model correctly predicts the temporal response from both undamaged rods and rods with machined simulated corrosion pits. The circuit model also accounts for loss, and the results show strong agreement with simulated soil-loss in laboratory experiments. Evidence of wave mode conversion is found in experimental data that is not captured by the model. Preliminary field measurements of copper-clad steel grounding rods are presented that show strong similarities to modeled results. This ECM is a promising basis for further development of pulse-echo systems for corrosion detection and may be useful for future tomographic analysis of field measurements.

Composite action between steel girders and concrete slab is an important mechanical feature that needs to be maintained so that bridges can carry the applied load safely. This mechanical feature is maintained through the shear studs installed at the top flange of the steel girders. These shear studs keep the steel girders and the concrete slab working as one unit, resulting in a stronger section than if each element works separately. The composite action can be investigated using several methods of which one is the study of the position of the neutral axis (NA). The variation of the position of the NA over time gives an indication about the structural performance of the composite section. In this study, the variation of the position of the NA over time is investigated. Two bridges located in Manitoba were investigated in this study. The variation of the NA is observed as a result of variation of ambient temperature (temperature). Regression models are suggested to relate variation of the NA to the temperature that was measured beside the web of one of the bridge girders. Repeatability analysis over 4 years was conducted, confirming that the NA varies cyclically over years. It is suggested that this variation indicates that there is a change in the degree of composite action assuming that cold temperatures will induce more connection between the steel girders and the concrete slab as a result of thermal contraction of the shear studs. In addition, the stiffness of the material could be affected due to change of temperature. The other possibility is that an axial force develops in the beam as a result of the bearing restraint during the passing of vehicles on the bridge. The results found in this study will eventually lead to enhancements of the design procedures that currently assume a fixed position of the NA over time of composite sections of bridges, similar to the bridges presented in this study.

In this work, we present an optical transit DEP flow cytometer for parallel single-cell analysis. Each cell's dielectric property is inferred from velocity perturbations due to DEP actuation in a microfluidic channel. Dual LED sources facilitate velocity measurement by producing two transit shadows for each cell passing through the channel. These shadows are detected using a 256-pixel linear optical array detector. Massively parallel analysis is possible as each pixel of the detector can independently analyze the passing cells. A wide channel (similar to 18 mm) was employed to carry many particles simultaneously, and the system was capable of detecting the velocity of over 200 cells simultaneously. We have achieved analysis rates for 10 mu m diameter polystyrene spheres response exceeding 250 per second. With appropriate calibration, this DEP cytometer can quantitatively measure the dielectric response. The dielectric response (Clausius-Mossotti factor) of viable CHO cells was measured over the frequency range of 100 kHz to 6 MHz, and the obtained response matches the previously measured values by our group. The DEP cytometer uses simple modular components to achieve high throughput label-free single-cell dielectric analysis and can begin analyzing particles within 10 s after starting to pump the sample into the channel.

Is the time now? When will SHM transition from a novelty to a decision support platform for Bridge Asset Management. Structural Health Monitoring has been used on major bridges and as a research tool for over 50 years. The instances of its application for long term continuous monitoring are in the 100’s. During this period the condition of the world’s inventory of bridges has steadily declined. Many industry experts are citing the need for better information to manage bridges in a more productive manner. The industry needs to transition to fact based decision making from engineering judgement based on visual inspection. Do those conditions exist now? How will the industry need to adapt to allow for mainstream implementation of measured performance and a timeline for this innovation. This talk will address the technical, organizational and economic requirements for SHM to become a true innovation and be put into successful and practical use as a tool for managing a bridge fleet over their life cycle. The technological state of SHM as of a couple of years ago and the application of internet of things (IoT) technology to structural health monitoring will be discussed. The minimization of required hardware and decentralized data management are some of the major innovations IoT brings to SHM. A case study involving the continuous monitoring of a fleet of 20 bridges is presented. Field data examples using live loads from traffic to estimate load distribution factors are shown. In addition histograms of traffic induced strains on simply supported short and medium span bridge are presented. Examples are presented of timber, prestressed concrete and steel girder bridges. In summary, continuous monitoring a fleet of bridges is now economically and technologically viable. Maybe some words about how data analysis is the future.